The present invention relates to an emission analysis method with an inductively-coupled radio frequency plasma as a source for emission analysis and an apparatus for use in such method and, more particularly, to an emission analysis method with an inductively-coupled radio frequency plasma as a source for emission analysis and an apparatus for use in such method to reduce a running costs.
Emission analysis is used when a sample is exposed to electrical or thermal energy, whereby, the spectra of emitted light from the sample are analysed by a spectroscope to obtain the spectra peculiar to elements contained in the sample. The presence and the strength of the spectra are measured to perform quantitative or qualitative analysis of the elements in the sample. In particular, an inductively-coupled radio frequency plasma (referred to as an ICP hereinafter) is suitable for performing the quantitative or qualitative analysis of a soldered sample as a source.
As a high frequency plasma for a source, the ICP is characterized in that a high frequency current less than 300M Hz flows through a coil to cause a high frequency magnetic field. According to the change of the high frequency magnetic field, an electromagnetic induction field is caused to discharge, whereby the combination of the discharge and an electric circuit becomes inductive. A light source of this type is called an ICP.
As compared with a spark or arc method as a source for emission analysis, the ICP system can afford a stable plasma and high precision of analysis. Conventionally, to maintain the stable generation of the plasma or continuously analyse a plurality of samples, a sample inlet system should be stabilized for each of the samples. Therefore, a gas inlet system to a plasma torch and a high frequency voltage source for generating a high frequency magnetic field are continuously operated in an appropriate analysis condition even without analysis taking place. It takes about 10-20 seconds to introduce a new sample into a plasma torch and analyze it. In comparison with the time necessary for analysis, the time necessary for stabilizing a plasma and the sample inlet system is extremely long, so that the necessary volume of argon gas to be introduced into the plasma torch and consumed therein is great, up to about 10-20 l/min and power consumption is also great, up to 10-2 kw/h. Since argon gas is expensive, running costs become extremely high.